This invention relates to injection molding, and more particularly to an extrusion assembly for dispensing or introducing a plastic material in fluid condition into an injection mold.
With an injection assembly in operative association, molding material is injected from an extrusion mechanism along an injection passageway into mold cavity through a sprue bore of the injection head. Generally, the mold material is allowed to solidify in the mold cavity whereupon the mold assembly is opened and the molded article removed.
Recently, a process has been advanced which produced a barrier container, i.e., a semi-rigid plastic container provided with a liner or inner layer of another material or materials having properties different than the outer layer thereof. In accordance with such process a performed liner or sleeve (manufactured, for example by thermoforming techniques) is positioned over a core rod with a parison or preform being subsequently formed about the liner in an injection station of an injection blow molding machine to form a composite container. As disclosed in co-pending application Ser. No. 448,191, filed Mar. 5, 1974 and assigned to the same assignee as the present invention, the composite parison is transferred to a blow mold for the expansion of such composite parison, as known by those skilled in the art.
Injection assemblies are capable of generating high pressures, e.g., the range of from about 2,000 to 10,000 psig., and depending on the plastic materials being used and characteristic thereof, the produced laminated container may be imperfect due to the shearing effects of the hot plastic material on the liner during formation of the composite parison in the injection mold.